NormalSubgroups( G )
NormalSubgroups
returns a list of all normal subgroups of G. The
subgroups are sorted according to their sizes.
gap> s4 := Group( (1,2,3,4), (1,2) );; s4.name := "s4";; gap> NormalSubgroups( s4 ); [ Subgroup( s4, [ ] ), Subgroup( s4, [ (1,2)(3,4), (1,4)(2,3) ] ), Subgroup( s4, [ (2,3,4), (1,3,4) ] ), Subgroup( s4, [ (3,4), (1,4), (1,2,4) ] ) ]
The default function GroupOps.NormalSubgroups
uses the conjugacy
classes of G and normal closures in order to compute the normal
subgroups.
GAP 3.4.4